Abstract:To explore the effects of sub-macrosarchitecture of different root systems on seedling growth, Pinus thunbergii seedlings were inoculated with three ectomycorrhizal fungi: Rhizopogen luteous (Rl), Pisolithus tinctorius (Pt2), and Boletus edulis (Be), respectively, to study the relationships of different ectomycorrhizal root architectures and the growth of Pinus thunbergii seedlings. Results showed that the root parameters (length of tap roots; total orders, numbers, and diameters of primary lateral roots; distribution range, number, and specific surface area (the ratio of surface area/volume) of absorptive roots) of Pinus thunbergii seedlings with three kinds of ectromycorrhizae increased at different degrees in comparison with non-inoculated seedlings (the control), and were positively correlated with the growth of P. thunbergii. The root architectures were significantly different among the seedlings with different ectomycorrhizal roots. In the root system of the seedlings with Rl, which grew best, the primary lateral root with different branching angles to tap roots were appropriately distributed. The ones with 80-90° branching angles were more than those with other branching angles and the lateral roots with branching angles of 60-80° and <60° decreased descendingly, which made the root system “heart-shaped”,and increased the uptaking spacial areas of the root system efficiently. The seedlings with Be grew relatively worse. Its root systems with different branching angles were not well distributed and the primary lateral roots with branching angles of 80-90° were less than those with other two ectomycorrhizal roots. The root architectures of the seedlings with Pt2 were between the ones with Rl and Be. The control seedlings developed the least roots, and almost no lateral roots with branching angles of 80-90°. Thus, ectoycorrhizal fungi had impact on the seedling growth of Pinus thunbergii by affecting the architectural development of its root systems.